Inertial measurement unit and movable device using the same

ABSTRACT

An inertial measurement unit includes a sensor and a heat preservation system. The heat preservation system includes a heat preservation body and a heat source. The sensor is positioned on the heat preservation body. The heat source is configured to generate heat. The heat preservation body is configured to transfer the heat from the heat source to the sensor to maintain a preset temperature in a space surrounding the sensor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/CN2015/093350 filed on Oct. 30, 2015, the entire contents of whichare incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an inertial measurement unit (IMU),and more particularly to an IMU and a movable device using the IMU.

BACKGROUND OF THE DISCLOSURE

Consumer unmanned aerial vehicles (UAVs) have been widely used invarious applications. Consumer UAVs are equipped with consumerMicro-ElectroMechanical System (MEMS) sensors. The characteristics ofconsumer MEMS sensors may be significantly influenced by a temperaturedrift, thus a temperature calibration is needed. A calibration oftemperature drift of MEMS sensors over a full temperature range can betime-consuming and inefficient. In addition, operating in an everchanging ambient temperature, the MEMS sensors may not provide stableand optimal characteristics.

SUMMARY OF THE DISCLOSURE

There is a need for an inertial measurement unit (IMU) having a constanttemperature heating functionality.

In addition, there is a need for a movable device having the IMU.

An aspect of the disclosure provides an inertial measurement unit (IMU)comprising one or more sensors and a heat preservation system configuredto maintain said one or more sensors at a preset temperature. The heatpreservation system can comprise a heat preservation body and aplurality of heat sources. The one or more sensors can be positioned onthe heat preservation body. The heat preservation system can generate aheat using the plurality of heat sources and transfers the heatgenerated from the plurality of heat sources to the one or more sensorsthrough the heat preservation body, such that the preset temperature canbe maintained surrounding the one or more sensors.

In some embodiments, the IMU can further comprise a circuit boardassembly, the circuit board assembly comprising a main body and anextension extending from a side of the main body.

In some embodiments, the main body can be a hollow frame formed byconnecting a plurality of flexible circuit boards and a plurality ofrigid circuit boards.

In some embodiments, the heat preservation body can be a polyhedralframe having a high thermal conductivity. A shape of the heatpreservation body can correspond to a shape of the main body of the IMUsuch that the heat preservation body can be accommodated within the mainbody of the IMU.

In some embodiments, the plurality of heat sources can be provided onand electrically connected to the circuit board assembly. The pluralityof heat sources can be disposed on a sidewall of the heat preservationbody.

In some embodiments, the plurality of heat sources can be disposed ontwo opposing sidewalls of the heat preservation body. A groove can beprovided on one or more sidewalls of the heat preservation body, suchthat the one or more sensors can be embedded in the groove provided onone or more sidewalls of the heat preservation body, which one or moresidewalls being adjacent to the two opposing sidewalls on which theplurality of heat sources can be disposed.

In some embodiments, the plurality of heat sources disposed on the twoopposing sidewalls of the heat preservation body can be evenlydistributed on a periphery of each of the sidewalls.

In some embodiments, the heat preservation body can be made of a metalhaving a high thermal conductivity. The IMU can further comprise a heatconductive member. The heat conductive member can be filled between theplurality of heat sources and the heat preservation body and between theone or more sensors and the heat preservation body to transfer a heat.

In some embodiments, the heat conductive member can be an electricallyinsulating and thermally conductive silicone.

In some embodiments, the heat preservation body can be enclosed withinthe main body of the circuit board assembly, such that the plurality ofheat sources can be brought into contact with the heat conductivemember, where the heat conductive member is fixed in advance to asidewall of the heat preservation body to be evenly distributed on twoopposing sidewalls of the heat preservation body, such that the heat canbe transferred to the heat preservation body.

In some embodiments, the heat preservation body can be a hexahedralframe. The heat preservation system can further comprise a plurality ofinsulation plates including a first insulation plate and a secondinsulation plate provided in a first direction and a third insulationplate and a fourth insulation plate provided in a second directionperpendicular to the first direction. The first insulation plate and thesecond insulation plate can sandwich the main body of the IMU in thefirst direction. The third insulation plate and the fourth insulationplate can sandwich the main body of the IMU in the second direction.

In some embodiments, the first insulation plate can comprise arectangular base plate and a first sidewall and a second sidewallrespectively extending downwardly and perpendicularly from two opposingsides of the rectangular base plate. The second insulation plate cancomprise a rectangular base plate and a third sidewall and a fourthsidewall respectively extending upwardly and perpendicularly from twoopposing sides of the rectangular base plate. The third insulation platecan comprise a rectangular base plate and a first stopper and a secondstopper respectively extending rightward and perpendicularly from amiddle of two opposing sides of the rectangular base plate. The fourthinsulation plate can comprise a rectangular base plate and a thirdstopper and a fourth stopper respectively extending leftward andperpendicularly from a middle of two opposing sides of the rectangularbase plate.

In some embodiments, a sum of a width of the first sidewall, a width ofthe third sidewall and a width of the first stopper can be substantiallyequal to a length of the main body in the first direction. A sum of alength of the first stopper and a length of the third stopper can besubstantially equal to a length of the main body in the seconddirection.

In some embodiments, the IMU can further comprise a first rubber piece,a second rubber piece and a casing. The first rubber piece can be fittedonto the first insulation plate and the second rubber piece can befitted onto the second insulation plate. The casing can integrate thefirst rubber piece, the second rubber piece and the main body as onepiece.

In some embodiments, a top of an inner wall of the first rubber piececan be grid-like, and a bottom of an inner wall of the second rubberpiece can be grid-like.

In some embodiments, the first rubber piece can comprise a rectangularrubber base plate and four sidewalls respectively extending downwardlyand perpendicularly from four sides of the rubber base plate. The secondrubber piece can comprise a rectangular rubber base plate and foursidewalls respectively extending upwardly and perpendicularly from foursides of the rubber base plate. The casing can comprise a rectangularbase plate and four sidewalls respectively extending downwardly andperpendicularly from four sides of the rectangular base plate.

In some embodiments, a notch can be provided on each of the foursidewalls of the casing. An opening can be provided on one sidewall ofthe casing from which the extension of the IMU can extend out.

Another aspect of the disclosure provides a movable device comprising aninertial measurement unit (IMU) described hereinabove.

Another aspect of the disclosure provides an inertial measurement unit(IMU) comprising a circuit board assembly having a main body. The IMUcan further comprise a cushioning piece configured to be fitted onto themain body to clamp the main body.

In some embodiments, the cushioning piece can comprise a first rubberpiece and a second rubber piece respectively fitted onto two oppositeends of the main body.

In some embodiments, a bottom of an inner wall of the second rubberpiece can be grid-like, and a top of an inner wall of the first rubberpiece can be grid-like.

In some embodiments, the IMU can further comprise a casing configured tointegrate the cushioning piece and the main body as one piece.

In some embodiments, the main body of the circuit board assembly can bea hollow rectangular frame formed by connecting a plurality of flexiblecircuit boards and a plurality of rigid circuit boards. The first rubberpiece can comprise a rectangular rubber base plate and four sidewallsrespectively extending downwardly and perpendicularly from four sides ofthe rubber base plate. The second rubber piece can comprise arectangular rubber base plate and four sidewalls respectively extendingupwardly and perpendicularly from four sides of the rubber base plate.The casing can comprise a rectangular base plate and four sidewallsrespectively extending downwardly and perpendicularly from four sides ofthe rectangular base plate.

In some embodiments, the circuit board assembly can further comprise anextension extending from a side of the main body. An opening can beprovided on one sidewall of the casing from which the extension of theIMU can extend out.

In some embodiments, a notch can be provided on each of the foursidewalls of the casing.

In some embodiments, the IMU can further comprise a plurality ofinsulation plates including a first insulation plate and a secondinsulation plate provided in a first direction and a third insulationplate and a fourth insulation plate provided in a second directionperpendicular to the first direction. The first insulation plate and thesecond insulation plate can sandwich the main body of the IMU in thefirst direction. The third insulation plate and the fourth insulationplate can sandwich the main body of the IMU in the second direction.

In some embodiments, the first rubber piece can be fitted onto the firstinsulation plate, and the second rubber piece can be fitted onto thesecond insulation plate.

Another aspect of the disclosure further provides a movable devicecomprising an inertial measurement unit (IMU) described hereinabove.

As compared with the prior art, in the inertial measurement unit (IMU)described hereinabove, an interior of the IMU can be heated efficientlyand stably to a constant temperature, such that defects in the prior artincluding a low heating efficiency, a poor temperature control effectand an impact of an adhesive stress can be effectively solved. With theheat preservation system of the IMU, the sensors of the IMU can bemaintained at the constant temperature and operate with a satisfactoryperformance in various external environments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded view of an inertial measurement unit (IMU) inaccordance with a first embodiment of the disclosure.

FIG. 2 shows positions of a heat source and a sensor of an IMU inaccordance with embodiments of the disclosure.

FIG. 3 shows an assembly of an IMU in accordance with some embodimentsof the disclosure.

FIG. 4 shows an exploded view of an IMU in accordance with a secondembodiment of the disclosure.

LIST OF REFERENCE NUMERALS

TABLE 1 Inertial measurement unit (IMU)  100 Circuit board assembly  101Main body 1010 Extension 1011 Sensor  102 Groove  103 Heat preservationbody  201 Heat conductive member  202 Heat source  203 First insulationplate  304a First sidewall  305a Second sidewall  306a Second insulationplate  304b Third sidewall  305b Fourth sidewall  306b Third insulationplate  304c First stopper  305c Second stopper  306c Fourth insulationplate  304d Third stopper  305d Fourth stopper  306d Casing  401Cushioning piece  402 First rubber piece  402a Second rubber piece  402bOpening  403 Notch  404 Fastener  501

Illustrative embodiments will be described in more detail by referenceto the drawings.

DETAILED DESCRIPTION OF THE DISCLOSURE

A better understanding of the disclosure will be obtained by referenceto the following detailed description that sets forth illustrativeembodiments with reference to the drawings. It will be apparent that theembodiments described herein are merely provided by way of example only.Those skilled in the art can conceive other embodiments in light ofthose embodiments disclosed herein without inventive efforts, and allthese embodiments are within the scope of the disclosure.

Illustrative embodiments of the disclosure will be described withreference to the drawings. The embodiments and features can be combinedwith one another provided that they are technically compatible.

FIG. 1 shows an exploded view of an inertial measurement unit (IMU) 100in accordance with a first embodiment of the disclosure is shown. TheIMU 100 can at least comprise one or more sensors 102 (two sensors areshown), a circuit board assembly 101, a heat preservation body 201, aheat conductive member 202 and a plurality of heat sources 203. In someembodiments, the heat preservation body 201, the heat conductive member202 and the plurality of heat sources 203 can serve as a heatpreservation system of the IMU 100 for providing a preset temperature tothe sensors 102.

In some embodiments, the sensor 102 can be a motion sensor (for example,a velocity sensor, such as a micro-electromechanical system (MEMS)accelerometer) and/or an attitude sensor (for example, atwo-axis/three-axis gyroscope). In some embodiments, the sensors 102 cancomprise two accelerometers and two gyroscopes.

The circuit board assembly 101 can comprise a main body 1010 and anextension 1011. The extension 1011 can extend from a side of the mainbody 1010. The main body 1010 can comprise a plurality of flexiblecircuit boards and a plurality of rigid circuit boards which are coupledto one another. Two adjacent rigid circuit boards can be connected by aflexible circuit board. The main body 1010 can be folded to enclose ahollow frame. In some embodiments, the rigid circuit boards can be PCBboards. In some embodiments, various electronic elements configured toimplement various functionalities of the IMU 100 can be provided on aninner surface of the main body 1010. In some embodiments, the main body1010 can be provided as a rectangular frame.

In some embodiments, the sensor 102 can be disposed on the main body1010 of the circuit board assembly 101 (for example, the sensor 102 canbe disposed on the rigid circuit board of the main body 1010) andelectrically connected to the circuit board assembly 101. The sensor 102can be provided within the heat preservation body 201. Referring to FIG.2, the sensor 102 can be disposed on the inner surface of the main body1010 of the circuit board assembly 101.

The extension 1011 can electrically connect the sensor 102 to externalelements (not shown) to transmit signals and/or power between thesensors 102 and the external elements. In some embodiments, theextension 1011 can be a flexible circuit board to facilitate aconnecting to the external elements.

It will be apparent that, the IMU 100 can comprise various functionalcomponents including a controller and at least one temperature sensor(not shown). In some embodiments, the controller can be disposed withinthe main body 1010 of the circuit board assembly 101, and thetemperature sensor can be provided within one of the sensors 102 (forexample, within at least one of the gyroscopes). Optionally, thecontroller can be disposed outside the main body 1010 of the circuitboard assembly 101 and electrically connected to the temperature sensorby the extension 1011 of the circuit board assembly 101. The temperaturesensor can sense an internal temperature of the IMU 100. If thetemperature is below a threshold, the controller can direct theplurality of heat sources 203 to generate a heat. The heat can betransferred to the sensors 102 through the heat conductive member 202and the heat preservation body 201, such that the internal temperatureof the IMU 100 can be maintained at a constant temperature. In this way,once a temperature calibration is performed at a single constanttemperature, the sensors 102 can be maintained at the constanttemperature and operate with a satisfactory performance in variousexternal environments.

In some embodiments, the heat preservation body 201 can be provided as apolyhedral frame having a high thermal conductivity. A shape of the heatpreservation body 201 can correspond to (for example, identical orsimilar to) a shape of the main body 1010, such that the heatpreservation body 201 can be accommodated within the main body 1010. Insome embodiments, a groove 103 can be provided on each sidewall of theheat preservation body 201, such that the sensor 102 and otherelectronic elements disposed on the inner surface of the circuit boardassembly 101 can be embedded in the heat preservation body 201 once theheat preservation body 201 is enclosed by the main body 1010 of thecircuit board assembly 101. In some embodiments, a sidewall of the heatpreservation body 201 does not need to include a groove 103 if no sensor102 or other electronic element is provided on a portion of the mainbody 1010 that corresponds to the sidewall of the heat preservation body201.

In some embodiments, the heat preservation body 201 can be made of ametal having a high thermal conductivity, such as aluminum, magnesium,silver or iron. In some embodiments, the heat preservation body 201 canbe made of a non-metal (for example, an insulation material). In someembodiments, the heat preservation body 201 can be provided as ahexahedral metal frame as shown in FIG. 1.

The heat conductive member 202 can be a thermally conductive siliconehaving a suitable shape and thickness. The heat conductive member 202can be filled between the plurality of heat sources 203 and the heatpreservation body 201 and between the sensor 102 and the heatpreservation body 201. In some embodiments, the heat conductive member202 can be an electrically insulating and thermally conductive silicone.In some embodiments, the heat conductive member 202 can be a heatconductive member having a high thermal conductivity, a high adhesionproperty and an electrical insulation property. The heat generated fromthe heat source 203 can be transferred to the heat preservation body 201through the heat conductive member 202. Meanwhile, the heat source 203can be electrically insulated from the heat preservation body 201. Theheat can be transferred from the heat preservation body 201 to thesensor 102 through the heat conductive member 202. Meanwhile, the heatpreservation body 201 can be electrically insulated from the sensors102. The heat preservation body 201 and the heat conductive member 202can serve as a thermal conducting layer of the IMU 101. The heatgenerated from the plurality of heat sources 203 can be transferred tothe sensors 102 through the heat preservation body 201 and the heatconductive member 202, such that the preset temperature can bemaintained in a surrounding of the sensor 102.

It will be appreciated that, the heat conductive member 202 can beomitted if the heat preservation body 201 is not made of a metal. Inthis case, the heat preservation body 201 can be made of an insulationmaterial having a high thermal conductivity.

The plurality of heat sources 203 can be disposed on the heatpreservation body 201 for producing heat. In some embodiments, theplurality of heat sources 203 can be provided at a plurality ofpredetermined positions on the inner surface of the main body 1010 ofthe circuit board assembly 101 (for example, the heat sources 203 can beprovided on the rigid circuit board of the main body 1010) andelectrically connected to the circuit board assembly 101. Referring toFIG. 2, the plurality of heat sources 203 can be symmetricallydistributed on two opposing sidewalls within the main body 1010.

In some embodiments, the heat conductive member 202 can be fixed to asidewall of the heat preservation body 201 in advance if the heatpreservation body 201 is a polyhedral frame made of metal. When the heatpreservation body 201 is enclosed within the main body 1010 of thecircuit board assembly 101, the plurality of heat sources 203 can bebrought into contact with the heat conductive member 202 and thus bedistributed on two opposing sidewalls of the heat preservation body 201(e.g., sidewalls on which the plurality of heat sources 203 aredisposed, hereinafter referred to “heating sidewalls”). The heatgenerated from the plurality of heat sources 203 can be transferred tothe heat preservation body 201 with the heat conductive member 202.

In some embodiments, the plurality of heat sources 203 can be aplurality of heating resistors. In some embodiments, the plurality ofheat sources 203 can be provided as any type of heat sources capable ofgenerating heat. The number of the plurality of heat sources 203 canvary in view of an actual structure of the IMU 100.

Referring to FIG. 1, once the heat preservation body 201 is enclosedwithin the main body 1010 of the circuit board assembly 101, theplurality of heat sources can be evenly distributed on a periphery ofeach of the two opposing sidewalls of the heat preservation body 201. Insome instances, four heat sources 203 can be distributed on each of thetwo opposing sidewalls of the heat preservation body 201. The four heatsources 203 can be symmetrically arranged on the periphery of thesidewall. It will be appreciated that, the four heat sources 203 do nothave to be symmetrically provided. Accordingly, the heat conductivemember 202, which is filled between the plurality of heat sources 203and the heat preservation body 201, can be provided with a hollowpolygonal shape to match the distribution of the plurality of heatsources 202. In this way, the heat conductive member 202 can contactwith the plurality of heat sources 203 to transfer the heat generatedfrom the heat sources 203 to the heat preservation body 201. The hollowpolygonal shape of the heat conductive member 202 can expose theelectronic elements disposed on the main body 1010 of the circuit boardassembly 101 from the heat conductive member 202.

In some embodiments, the sensor 102 can be disposed at a predeterminedposition of the main body 1010 of the circuit board assembly 101 toenable an uniform heat transmission from the plurality of heat sources203 to the sensor 102. For instance, the sensor 102 can be disposed suchthat the sensor 102 is positioned on the heat preservation body 201 whenthe heat preservation body 201 is enclosed within the main body 1010 ofthe circuit board assembly 101. In some instances, the sensor 102 can beembedded in a groove 103 provided on a sidewall of the heat preservationbody 201, which sidewall being adjacent to the two opposing heatingsidewalls on which the plurality of heat sources 203 are disposed. Asshown in FIG. 1, among the hexahedral heat preservation body 201, thereare four sidewalls adjacent to the two opposing heating sidewalls onwhich the plurality of heat sources 203 are disposed. In other words,four sensors 102 can be embedded in the grooves 103 provided on the foursidewalls adjacent to the two opposing heating sidewalls.

In some embodiments, the sensors 102 can comprise a first accelerometer,a second accelerometer, a first gyroscope and a second gyroscope. Asshown in FIG. 1, the sensor 102, which can be embedded in a sidewall ofthe heat preservation body 201, can be the first accelerometer, and thesecond accelerometer can be embedded in a groove 103 provided on abottom surface of the hear conducting heat preservation body 201. Asshown in FIG. 1, the sensor 102 embedded in a groove 103 provided on atop surface of the heat preservation body 201 can be the firstgyroscope, and the second gyroscope can be embedded in a groove 103provided on a sidewall of the heat preservation body 201 opposite to thesidewall on which the first accelerometer is disposed. The sides onwhich the sensors 102 are disposed can be adjacent to the two opposingheating sides, such that the heat generated from the plurality of heatsources 203 can be efficiently and uniformly transferred into thesidewalls of the grooves 103 which receive the sensors 102. A structureof the IMU 100 can have a compact structure and a reduced volume bydisposing the sensors 102 within the grooves 103.

The heat generated from the plurality of heat sources 203 can betransferred to the heat preservation body 201 through the heatconductive member 202. Subsequently, the heat can be transferred to thesidewalls in which the sensors 102 are embedded through the heatpreservation body 201. Then, the heat can be transferred to the sensors102 through the heat conductive member 202. In some embodiments, if theinternal temperature of the IMU 100 as sensed by the temperature sensorof the IMU 100 is below a preset temperature threshold, the controllerof the IMU 100 can direct the plurality of heat sources 203 to generateheat. The heat generated from the plurality of heat sources 203 can beefficiently and uniformly transferred to the sensors 102 through athermal conduction path “the heat sources—the heat conductive member—theheat preservation body—the heat conductive member—the sensors”, suchthat a constant temperature operating environment is created for thesensors 102. In this way, once a temperature calibration is performed ata single constant temperature, the sensors 102 can operate with asatisfactory performance in various external environments.

In some embodiments, the IMU 100 can further comprise a first insulationplate 304 a, a second insulation plate 304 b, a third insulation plate304 c and a fourth insulation plate 304 d. The plurality of insulationplates can enclose the sensors 102, the plurality of heat sources 203,the heat preservation body 201 and the main body 1010 of the circuitboard assembly 101.

It will be appreciated that, the four insulation plates as discussedhereinabove are provided where the main body 1010 is a rectangular framelike. In some embodiments, the number of the plurality of insulationplates can vary to fit a shape of the main body 1010. In someembodiments, the first insulation plate 304 a, the second insulationplate 304 b, the third insulation plate 304 c and the fourth insulationplate 304 d can serve as a peripheral heat preservation layer enclosingthe heat preservation body 201 and the circuit board assembly 101, suchthat an internal temperature of the IMU 100 can be further maintainedconstant. In some embodiments, the first insulation plate 304 a and thesecond insulation plate 304 b can be provided in a first direction(shown as a y-direction) to sandwich the circuit board assembly 101 ofthe IMU 100 in the first direction. The third insulation plate 304 c andthe fourth insulation plate 304 d can be provided in a second direction(shown as an x-direction) to sandwich the circuit board assembly 101 ofthe IMU 100 in the second direction. The first direction can beperpendicular to the second direction. The first insulation plate 304 a,the second insulation plate 304 b, the third insulation plate 304 c andthe fourth insulation plate 304 d can enclose the main body 1010 of theIMU 100 by clamping the circuit board assembly 101 as discussedhereinabove. The insulation plates can insulate an external heat if anexternal temperature is high. On the other hand, the insulation platescan maintain a temperature by preventing an heat dissipation from theIMU 100 if the external temperature is low.

In some embodiments, the first insulation plate 304 a can comprise arectangular base plate and a first sidewall 305 a and a second sidewall306 a respectively extending downwardly and perpendicularly from twoopposing sides of the rectangular base plate. A width of the firstsidewall 305 a can be identical to a width of the second sidewall 306 a.In some embodiments, the width of the first sidewall 305 a can bedifferent from the width of the second sidewall 306 a. The secondinsulation plate 304 b can comprise a rectangular base plate and a thirdsidewall 305 b and a fourth sidewall 306 b respectively extendingupwardly and perpendicularly from two opposing sides of the rectangularbase plate. A width of the third sidewall 305 b can be identical to awidth of the fourth sidewall 306 b. In some embodiments, the width ofthe third sidewall 305 b can be different from the width of the fourthsidewall 306 b. In some embodiments, the widths of the first sidewall305 a, the second sidewall 306 a, the third sidewall 305 b and thefourth sidewall 306 b can be identical.

The third insulation plate 304 c can comprise a rectangular base plateand a first stopper 305 c and a second stopper 306 c respectivelyextending rightward and perpendicularly from a middle of two opposingsides of the rectangular base plate. A width of the first stopper 305 ccan be identical to a width of the second stopper 306 c. In someembodiments, the width of the first stopper 305 c can be different fromthat of the second stopper 306 c. The fourth insulation plate 304 d cancomprise a rectangular base plate and a third stopper 305 d and a fourthstopper 306 d (not show in the figures as being blocked) respectivelyextending leftward and perpendicularly from a middle of two opposingsides of the rectangular base plate. A width of the third stopper 305 dcan be identical to a width of the fourth stopper 306 d, and a length ofthe third stopper 305 d can be identical to a length of the fourthstopper 306 d. In some embodiments, the width/length of the thirdstopper 305 d can be different from the width/length of the fourthstopper 306 d. In some embodiments, the widths of the first stopper 305c, the second stopper 306 c, the third stopper 305 d and the fourthstopper 306 d can be identical.

In some instances, a sum of the width of the first sidewall 305 a, thewidth of the third sidewall 305 b and the width of the first stopper 305c or the third stopper 305 d can be substantially equal to or slightlygreater than a length of the main body 1010 in the first direction, andthe sum of the length of the first stopper 305 c and the length of thethird stopper 305 d can be substantially equal to or slightly greaterthan a length of the main body 1010 in the second direction. Therefore,a complete enclosure of the circuit board assembly 101 can be effected.

FIG. 3 shows an assembly of an IMU in accordance with some embodimentsof the disclosure. In some embodiments, the first insulation plate 304a, the second insulation plate 304 b, the third insulation plate 304 cand the fourth insulation plate 304 d can be integrally fastened to thecircuit board assembly 101 of the IMU 100 and the heat preservation body201 using a plurality of fasteners 501. In some embodiments, theplurality of fasteners 501 can be screws. In some embodiments, theplurality of fasteners 501 can be other types of locking members capableof fastening the IMU 100.

It will be appreciated that, when the plurality of insulation plates,the circuit board assembly 101 and the heat preservation body 201 areassembled using the screws, two or more screw holes can be provided onthe rectangular base plates of the insulation plates, and two or morecorresponding screw holes can be provided on a corresponding side of thecircuit board assembly 101 and the heat preservation body 201, such thatthe locking screws can pass through those screw holes to effect thefastening. Referring to FIGS. 1-2, in some embodiments, the two screwholes can be provided along a diagonal line of the rectangular baseplate of the insulation plate.

In some embodiments, the IMU 100 can be provided to a movable deviceincluding a vehicle, a watercraft and an unmanned aerial vehicle (UAV).

FIG. 4 shows an exploded view of an IMU in accordance with a secondembodiment of the disclosure is shown. In addition to the configurationof the first embodiment, the IMU 100 in accordance with the secondembodiment can further comprise a casing 401 and a cushioning piece 402.In the second embodiment, the heat preservation body 201, the heatconductive member 202 and the plurality of heat sources 203 can beomitted from the IMU 100.

In some embodiments, the cushioning piece 402 can be made of a flexiblebut tough material to improve a vibration reduction of the IMU 100. Insome embodiments, the cushioning piece 402 can comprise a first rubberpiece 402 a and a second rubber piece 402 b. In some embodiments, thefirst rubber piece 402 a can comprise a rectangular rubber base plateand four sidewalls extending downwardly and perpendicularly from foursides of the rubber base plate. For instance, the first rubber piece 402a can be a rectangular cover like. The second rubber piece 402 b cancomprise a rectangular rubber base plate and four sidewalls extendingupwardly and perpendicularly from four sides of the rubber base plate.For instance, second rubber piece 402 b can be a rectangular cover like.In some embodiments, a shape of the rubber base plates of the firstrubber piece 402 a and the second rubber piece 402 b can vary to fit theshape of the main body 1010, as long as the first rubber piece 402 a andthe second rubber piece 402 b can be fitted onto the main body 1010. Thefirst rubber piece 402 a can be fitted onto the first insulation plate304 a. The second rubber piece 402 b can be fitted onto the secondinsulation plate 304 b.

In some embodiments, the casing 401 can be fitted onto the first rubberpiece 402 a and the second rubber piece 402 b, such that the firstrubber piece 402 a, the second rubber piece 402 b and the IMU 100 can beintegrated as one piece. The circuit board assembly 101 of the IMU 100can be completely enclosed using the first insulation plate 304 a, thesecond insulation plate 304 b, the third insulation plate 304 c, thefourth insulation plate 304 d, the casing 401, the first rubber piece402 a and the second rubber piece 402 b. Therefore, heat can beinsulated from surrounding environment, and meanwhile, a heatdissipation from the IMU 100 can be prevented.

In some embodiments, a bottom of an inner wall of the second rubberpiece 402 b and a top of an inner wall of the first rubber piece 402 acan be grid-like. The grids can be soft and deformable therebetween. Thecasing 401 can comprise a rectangular base plate and four sidewallsrespectively extending downwardly and perpendicularly from four sides ofthe rectangular base plate. A notch 404 can be provided on each of thefour sidewalls to facilitate a fitting of the casing 401 onto thecushioning piece 402 or a removal the casing 401 from the cushioningpiece 402. In some embodiments, an opening 403 can be provided on onesidewall of the casing 401 from which the extension 1011 of the IMU 100can extend out. With the first insulation plate 304 a, the secondinsulation plate 304 b, the third insulation plate 304 c, the fourthinsulation plate 304 d, the casing 401, the first rubber piece 402 a andthe second rubber piece 402 b, an internal temperature of the IMU 100can be maintained constant while a vibration reduction of the IMU 100can be further improved.

It will be appreciated that, a length of the casing 401 in the firstdirection (shown as y-direction, a direction perpendicular to the firstinsulation plate 304 a) can be identical to a length of the main body1010 of the IMU 100 in the first direction, such that the first rubberpiece 402 a and the second rubber piece 402 b are prevented fromdetaching from the IMU 100 under vibration and the IMU 100 can be betterpositioned. In this way, an accuracy in assembling the IMU 100 can beimproved.

In some embodiments, the first rubber piece 402 a and the second rubberpiece 402 b can be fitted respectively onto two opposite ends of themain body 1010, such that the main body 1010 can be sandwiched betweenthe first rubber piece 402 a and the second rubber piece 402 b. In someembodiments, the first rubber piece 402 a and the second rubber piece402 b can directly abut each other, such that the main body 1010 can becompletely enclosed. In some embodiments, the first rubber piece 402 aand the second rubber piece 402 b can be separated by a distance.

The above description merely illustrates some embodiments of thedisclosure and is not intended to limit the scope of the disclosure. Anyequivalent changes in structures or processes made in light of thespecification and the drawings, and their direct or indirect applicationin other related technical fields should all be encompassed in the scopeof the present disclosure.

What is claimed is:
 1. An inertial measurement unit (IMU) comprising: asensor; and a heat preservation system including: a heat preservationbody; and a heat source; wherein: the sensor is positioned on the heatpreservation body; the heat source is configured to generate heat; andthe heat preservation body is configured to transfer the heat from theheat source to the sensor to maintain a preset temperature in a spacesurrounding the sensor.
 2. The IMU of claim 1, further comprising: acircuit board assembly including a main body and an extension extendingfrom a side of the main body.
 3. The IMU of claim 2, wherein the mainbody includes a hollow frame formed by a plurality of flexible circuitboards and a plurality of rigid circuit boards connected together. 4.The IMU of claim 3, wherein: the heat preservation body includes apolyhedral frame having a high thermal conductivity; and a shape of theheat preservation body corresponds to a shape of the main body.
 5. TheIMU of claim 4, wherein: the heat source is provided on and electricallyconnected to the circuit board assembly; and the heat source is disposedon a sidewall of the heat preservation body.
 6. The IMU of claim 5,wherein: the heat source is a first heat source and the sidewall is afirst side wall of the heat preservation body; the heat preservationsystem further includes a second heat source disposed on a secondsidewall of the heat preservation body that is opposite to the firstside wall; and the sensor is embedded in a groove on a third sidewall ofthe heat preservation body that is adjacent to the two first sidewalland the second sidewall.
 7. The IMU of claim 6, wherein: the heatpreservation system further includes one or more third heat sources andone or more fourth heat sources; the first heat source and the one ormore third heat sources are disposed evenly on a periphery of the firstsidewall; and the second heat source and the one or more fourth heatsources are disposed evenly on a periphery of the second sidewall. 8.The IMU of claim 4, wherein the heat preservation body is made of ametal having a high thermal conductivity; the IMU further comprising: aheat conductive member filled between the heat source and the heatpreservation body and between the sensor and the heat preservation body.9. The IMU of claim 8, wherein the heat conductive member includes anelectrically insulating and thermally conductive silicone.
 10. The IMUof claim 8, wherein the heat preservation body is enclosed within themain body and the heat source contacts the heat conductive member. 11.The IMU of claim 4, wherein: the heat preservation body includes ahexahedral frame; the heat preservation system further includes: a firstinsulation plate and a second insulation plate provided in a firstdirection and sandwiching the main body in the first direction; and athird insulation plate and a fourth insulation plate provided in asecond direction perpendicular to the first direction and sandwichingthe main body in the second direction.
 12. The IMU of claim 11, wherein:the first insulation plate includes: a first rectangular base plate; anda first sidewall and a second sidewall respectively extending downwardlyand perpendicularly from two opposing sides of the first rectangularbase plate; the second insulation plate includes: a second rectangularbase plate; and a third sidewall and a fourth sidewall respectivelyextending upwardly and perpendicularly from two opposing sides of thesecond rectangular base plate; the third insulation plate includes: athird rectangular base plate; and a first stopper and a second stopperrespectively extending rightward and perpendicularly from a middle oftwo opposing sides of the third rectangular base plate; and the fourthinsulation plate includes: a fourth rectangular base plate; and a thirdstopper and a fourth stopper respectively extending leftward andperpendicularly from a middle of two opposing sides of the fourthrectangular base plate.
 13. The IMU of claim 12, wherein: a sum of awidth of the first sidewall, a width of the third sidewall and a widthof the first stopper is substantially equal to a length of the main bodyin the first direction; and a sum of a length of the first stopper and alength of the third stopper is substantially equal to a length of themain body in the second direction.
 14. The IMU of claim 11, furthercomprising: a first rubber piece fitted onto the first insulation plate;a second rubber piece fitted onto the second insulation plate; and acasing integrating the first rubber piece, the second rubber piece, andthe main body as one piece.
 15. The IMU of claim 14, wherein a top of aninner wall of the first rubber piece is grid-like, and a bottom of aninner wall of the second rubber piece is grid-like.
 16. The IMU of claim14, wherein: the first rubber piece includes a rectangular rubber baseplate and four sidewalls respectively extending downwardly andperpendicularly from four sides of the rubber base plate; the secondrubber piece includes a rectangular rubber base plate and four sidewallsrespectively extending upwardly and perpendicularly from four sides ofthe rubber base plate; and the casing includes a rectangular base plateand four sidewalls respectively extending downwardly and perpendicularlyfrom four sides of the rectangular base plate.
 17. The IMU of claim 16,wherein; each of the four sidewalls of the casing includes a notch; andone sidewall of the casing includes an opening from which the extensionof the IMU extends out.
 18. A movable device comprising: an inertialmeasurement unit (IMU) including: a sensor; and a heat preservationsystem including: a heat preservation body; and a heat source; wherein:the sensor is positioned on the heat preservation body; the heat sourceis configured to generate heat; and the heat preservation body isconfigured to transfer the heat from the heat source to the sensor tomaintain a preset temperature in a space surrounding the sensor.
 19. Themovable device of claim 18, wherein the IMU further includes a circuitboard assembly including a main body and an extension extending from aside of the main body.
 20. The movable device of claim 19, wherein themain body includes a hollow frame including a plurality of flexiblecircuit boards and a plurality of rigid circuit boards connectedtogether.